Apparatus and process for removing metallic particles from effluent liquid waste

ABSTRACT

An apparatus for separating solid particles from the suction effluent of, for example, a dental office, preferably driven by a dental office vacuum pump, includes a surge tank for accommodating effluent overfill connected to a sedimentary deposit tank for sedimentation of effluent particles. A bypass conduit is connected to the surge tank inlet which is equipped with a vacuum break valve for allowing air into the system when the suction openings are closed. The sedimentary deposit tank has a series of baffle chambers through which effluent flows in sequence, and in each of which chambers sediment is deposited for later removal. The surge tank preferably has a liquid level sensor and warning device. Modular filters or adsorbants may be installed in the sedimentary deposit tank, or a modular auxiliary filter may be connected downstream of the tank. Chemical injection may be used to improve sedimentation. A positive air pressure source or auxiliary pumps may be used to drive the effluent, particularly in large installations incorporating multiple surge and deposit tanks. Full tank effluent removal and drying facilities are optionally provided.

RELATED APPLICATION DATA

[0001] The present patent application is a continuation-in-part of PCTInternational Patent Application No. PCT/CA99/00665 filed on Jul. 21,1999 that designates the United States and that claims priority fromCanadian patent application No. 2,243,580, filed on Jul. 24, 1998.

FIELD OF THE INVENTION

[0002] This invention relates to methods and apparatus suitable toremove particles from effluent waste, and particularly, to removeamalgam and other metallic particles and other abrasive solids fromdental office suction effluent.

BACKGROUND OF THE INVENTION

[0003] Although amalgams are less frequently used for new dentalfillings than was the case some decades ago, nevertheless, amalgamscontinue to comprise a significant portion of the metallic particlecomponent of dental office effluent because of the fact that oldfillings comprising amalgams are drilled out and removed in the effluentwaste when new fillings are effected to replace the old. Further, evenunder current dental practice, an amalgam is preferred for some toothfilling situations. The use of an amalgam in a filling is never a 100%efficient process; amalgam residues are discharged into the dentaloffice effluent. Typically, dental amalgam comprises a number of metals,invariably of course including mercury and almost always at least somesilver. Because mercury is a poison that can accumulate in livingtissues and can pose a health hazard to species in a food chain exposedto mercury-containing compounds, and since humans are inevitably at theend of the food chain, it follows that effluent containing amalgams canpose a health hazard to the community at large. Also, certain metalssuch as silver are commercially valuable if recovered in quantity. Forthose reasons, it is desirable to devise apparatus and processes forremoving amalgams from dental office effluent. In addition to removingamalgams, other matter disposed into dental office suction effluentincludes aluminum oxides used in air abrasion treatments and other solidwaste material. These solid materials tend to wear out or damage vacuumpumps and other equipment downstream of the dental chair suctionapparatus, and also constitute effluent water contaminants. Therefore,it is desirable for the apparatus to remove solid abrasive material andother particulate waste from the dental office suction effluent.

[0004] Previously known apparatus for removing amalgam particles fromdental office suction effluent are known to include a collecting tankfor collecting a working day's accumulation of suction effluent from oneor more sources of such waste. The waste is sucked from the dental chairsuction apparatus and into the collecting tank by a vacuum pump. Whenthe vacuum pump is turned off, an outlet valve is opened and theaccumulated waste is deposited into a separation device intended toseparate metal particles from the effluent liquid. Flow into theseparation device is induced by the head of fluid in the collectingtank. Particles passing through the separation device are separated fromthe waste by gravity and settle to the bottom of the separation device.The flow rate is dependent on the head inside the collecting tank; asthe head diminishes, the flow rate also diminishes. The changes in flowrate are undesirable because the particle separation rate is affected,and the system becomes prone to plugging when the flow rate decreases.Also, since the waste can be deposited only when the vacuum pump is off,waste is usually moved to the separation device at the end of the day.As a result, the collecting tank and separation device tend to beundesirably large.

[0005] Another known apparatus is a centrifuge type system thatseparates heavier metal particles from effluent liquid by collecting theparticles at the peripheral wall of the centrifuge. This apparatus doesnot effectively separate lighter particles, and is expensive to purchaseand operate due to the complexity of its mechanical parts.

[0006] Yet another known apparatus uses a dedicated mechanical pump tosuction waste liquids through a separator device. Again, a dedicatedpump can be expensive to purchase and to maintain, and can beundesirably space-consuming.

[0007] Such known systems can become quite complex, unwieldy andexpensive, as for example that disclosed in Ralls U.S. Pat. No.5,885,076 granted Mar. 23, 1999. Ralls teaches the use of sedimentation,co-precipitation and filtration in an expensive complicated apparatusthat is probably economical, if at all, only for relatively largeinstallations such as a military base dental complex.

[0008] An alternative approach described in Ludvigsson U.S. Pat. No.5,205,743 granted Apr. 27, 1993 involves provision of an air flow in thevicinity of the patient's mouth and suction from that air flow; suchapparatus is designed to remove mercury vapour present in the air flow.

[0009] The present invention overcomes some of the shortcomings of theprior technology and achieves further advantages that will be apparentafter reviewing the following summary of the invention and detaileddescription.

SUMMARY OF THE INVENTION

[0010] According to the invention, an apparatus is provided for removingmetal-containing particles and other waste particles from effluent,particularly effluent from a dental office. While herein the term “metalparticles” will frequently be employed, it is contemplated that theapparatus is fully capable of separating other solid particles fromeffluent liquid. Further, with the aid of one or more precipitants,selected solutes may also be removed. In a particular application to bedescribed in detail, effluent from a dental office suction apparatus isdiscussed; the metal particles are primarily amalgam particles made ofmercury and silver alloyed together in an amalgam composition, sometimeswith other metals. The metal particles may be in solid particulate formsuspended in the liquid, or may be in solute form dissolved in theliquid. The solid particles other than amalgam residues include aluminumoxides used in air abrasion treatment, enamel and dentin from teeth,porcelain, acrylic used in bridges, and prosthetic cementing agents suchas zinc phosphate cement used in crowns and bridges. These solidparticles are typically suspended in the liquid effluent. Herein suchparticles are sometimes collectively referred to as “target particles”,since they are targeted for removal from the effluent. Such targetparticles also include precipitated particles obtained in the effluentsuspension by precipitation of solutes out of solution.

[0011] According to one aspect of the invention, an apparatus forremoving metal particles and other solid particles from liquid suctioneffluent can be installed in a dental office using a pre-existingsuction/vacuum pump system to provide fluid flow through the apparatus,without requiring dedicated fluid-flow provenance devices. The apparatusmay share a common vacuum pump with conventional dental chair suctionapparatus, without interrupting the use of suction equipment at thedental chairs.

[0012] Removal of solid particles from liquid suction effluent may beeffected by a combination of sedimentation and filtration, assisted byflocculation and precipitation. The invention is not concerned with thespecific choice of sedimentary deposit apparatus, a preferredimplementation being presented herein as a suitable exemplification ofsuch apparatus. Nor is the invention concerned with specific choices ofprecipitants, coagulants, flocculants, or other associated materials toeffect or facilitate removal of solids or solutes; rather, the inventionis concerned with the overall system of solids removal, the provision ofapparatus and methods for controlling flow of liquids and gases therein,and the facilitation of removal and replacement of deposit tanks thathave been filled with solid waste.

[0013] In accordance with a preferred embodiment of the invention, thedental office suction effluent is passed from dental chair suctionequipment outlets to a surge tank via a suitable inlet port for thesurge tank. The surge tank in turn passes effluent into a sedimentarydeposit tank, closed on all sides when in use and preferably readilydetachable for emptying and replacement. The sedimentary deposit tank ina preferred embodiment has a series of interior walls that separate theinterior of the sedimentary deposit tank into a consecutive series ofbaffle chambers, including an inlet baffle chamber at the beginning ofthe series and an outlet baffle chamber at the end of the series. Theinlet baffle chamber receives effluent through an inlet port, situatedin the preferred embodiment in the lid of the sedimentary deposit tank.The baffle chambers in between the inlet and outlet baffle chambers eachin turn receive effluent passed to such chamber by the preceding suchbaffle chamber in the series. So, liquid effluent flows from the inletbaffle chamber through the interconnected series of baffle chambers tothe outlet baffle chamber from whence it passes via a deposit tankoutlet port, and preferably thence to an auxiliary filtration unit, aswill be further described below.

[0014] In such preferred sedimentary deposit tank, each baffle chamber,or at least some of them, receive removable baffles composed of inverseV-shaped strips, inclined either in one dimension, resembling a chevron,or in two dimensions, resembling a gable in appearance. Such baffles arearranged and joined to form channels bounded above and below by thebaffle or sedimentary tank surfaces and the side walls of which areformed by the interior divider walls of the baffle chamber into whicheach baffle is individually inserted. Further, the transverse width ofeach baffle must be less than the transverse width of the sedimentarydeposit tank such that after the insertion and centering of the baffleinside the corresponding baffle chamber, there are apertures between theside walls of the sedimentary tank and the edges of the baffles to allowfor the effluent to access and exit the channels formed by the bafflesand baffle chamber walls.

[0015] In a preferred embodiment of the invention designed to minimizemanufacturing costs, the baffles in the baffle chambers are individuallyformed, configured and dimensioned so that they can be verticallystacked on top of each other or aligned end to end within the bafflecompartment. In another preferred embodiment of the invention designedto minimize the costs of assembling sedimentary tank equipment, severalvertically spaced baffles are integrally formed as a unit, theconfiguration and dimensions of such integral baffle units and thebaffle compartments selected so that just one integral baffle unit fitsinto each compartment. Such chevron or gable-shaped baffles ormulti-surface integral baffle units can be cheaply and easilymanufactured in quantity and simply inserted into a mating bafflecompartment without requiring any fasteners, and removed just as easilyfor cleaning or replacement. In a further embodiment of the inventionthat provides for additional effluent flow paths through an individualbaffle chamber thus promoting efficient sedimentation, two sets ofinclined baffle surfaces, each of approximately half the width of anindividual baffle chamber, may be fixedly attached on opposite sides ofa vertical dividing wall to provide a single unit that can be removablyinserted into a compartment of the sedimentary deposit tank.Alternatively, in the interest of modular design, baffle surfaces may befixedly attached to the baffle chamber walls, such walls being designedto be easily removable from the sedimentary deposit tank for cleaning orreplacement of the fixedly attached baffle surfaces.

[0016] Each transverse baffle chamber wall of the preferred sedimentarydeposit tank separating each baffle chamber from its neighbouringchamber or chambers, extends from the floor of the chamber to a top edgeof the chamber and has a notch on its top edge. The bottom edge of eachnotch is positioned on a pass-over height that is common to all of thechambers. As described above, the water successively enters, passesthrough the baffle channel and exits each baffle chamber; accordingly,for the baffle chamber to be functional, the horizontal position of theopenings (comprising notches and inlet and outlet ports) in each twoneighboring chambers must alter in transverse position, so the fluid canenter each chamber on one side, pass through the channel formed by thebaffle and exit the chamber on the other end. Because all the notches inone sedimentary deposit tank are preferably at the same vertical level,the second baffle chamber (the neighbour to the inlet baffle chamberimmediately downstream thereof) can receive liquid only when the inletbaffle chamber is full and liquid passes over the notch on theintervening transverse baffle chamber wall once it has reached thepass-over height. Similarly, liquid can pass from the second bafflechamber to the third only after the second baffle chamber is full andliquid passes over the notch on top of the wall of the second chamber atthe pass-over height to enter the third baffle chamber, and so forth upto the final outlet baffle chamber. When the outlet chamber becomesfull, it passes liquid out of the sedimentary deposit tank via theoutlet port. In a preferred embodiment of the present invention, thebaffle chamber walls are integrally formed as a fixed part of thesedimentary tank structure. Alternatively, however, the baffle chamberwalls may be separately formed and removably configured to engage slotsin the walls and floor of the sedimentary deposit tank, the slotsholding such baffle chamber walls in place inside the sedimentarydeposit tank. Optionally, inclined baffle surfaces may be fixedlyattached to such removable baffle chamber walls, as mentioned above.

[0017] In each baffle chamber, the target particles, being on theaverage heavier than the liquid effluent, will tend to sink to thebottom of the baffle chamber. Those target particles that are notcollected in the first baffle chamber have a chance to be collected inthe second, and so on in sequence to the final outlet baffle chamber, sothat overall there is a good chance that at least the heavier targetparticles will be collected at the bottom of the various bafflechambers. Further particle separation can be effected by passing thesuction effluent through a plurality of screens or filters positioned insome of the baffle chambers. In a preferred embodiment of the invention,such screens or filters may be located in the final (downstream) bafflechamber or final few baffle chambers to remove particles remaining inthe effluent after sedimentation in upstream baffle chambers has takenplace before effluent exits the sedimentary deposit tank. Removal ofdissolved solute metal particles from the effluent liquid can beachieved by adding a suitable chemical agent such as a precipitant,chelating agent or coagulant, or some combination thereof to theeffluent being processed in the sedimentary deposit tank, such chemicalagent(s) being selected for combination with solute mercury or silver orboth, it being an important objective to remove solute mercuryparticles, and an objective also to remove solute silver particles fromthe effluent. The chemical agent precipitates out of the solution metalparticles that are in solute form and may facilitate formation of largerparticles from smaller particles. Among suitable such agents areprecipitants such as potassium iodide (KI), potassium iodate (KIO₃),sodium sulfide (Na₂S) and various other sulfur compounds; a preferredchelating agent is sodium ethylenediaminetetraacetic acid (sodium EDTA).

[0018] The chemical agent(s) may conveniently be injected into theeffluent being processed in the sedimentary deposit tank by means of oneor more inlet ports preferably located at or near the top of the secondor third baffle chamber so that after the largest particles have settledout of solution in the first or second baffle chambers, the chemicalagent(s) may act on the entirety of the liquid passing through theremaining downstream baffle chambers in sequence.

[0019] If desired, a time-dependent delivery apparatus may provide ametered amount of chemical agent via one or more inlet ports to thesecond or third baffle chamber, or the chemical agent(s) may be added ona flow-rate-dependent basis, as preferred. The amount of agent added perunit of time or per unit of effluent flow will be dependent in part uponthe chemical characteristics of the agent(s) employed, and in part uponthe expected concentration of particles in the effluent liquid, and isusually best determined empirically. Accordingly, the amount of chemicalagent added to the settlement tank baffle chamber per unit of time orper unit of effluent passing through the baffle chamber is preferablyadjustable. According to one aspect of the invention, the introductionof such chemical agent(s) is automatically regulated to occur only whenthe dental office suction apparatus is operating actively; an overnightshutdown will occur without intervention.

[0020] As an alternative to or in combination with the addition ofchemical agents such as precipitants, flocculants and chelating agentsto the effluent, an adsorbent compound may be used to remove metal ionsfrom solution by surficial adsorption. Such a compound may beincorporated in the construction of the interior of the systemsettlement tank whereby metal ions dissolved in the effluent passingthrough the tank are adsorbed by the adsorbent material. A preferredadsorbent material is bentonitic clay. In a preferred embodiment of thepresent invention, finely divided bentonite clay particles are combinedwith activated silica particles and enclosed in a porous and permeablemembrane, similar in function and appearance to a tea bag. Suchbentonite and silica filled membrane may preferably be located in thefinal few baffle chambers of the sedimentary deposit tank wherebydissolved mercury and other metal ions may be adsorbed by the bentonite,and organic compounds may be adsorbed by the silica prior to theeffluent exiting the tank through the tank exit port.

[0021] In order to control the growth of bacteria, yeasts, molds, fungiand viruses in the effluent treatment system, a disinfectant is added tothe effluent at the individual operatory suction openings. In thepreferred embodiment of the invention, the disinfectant is chlorine,bromine or peroxide based, and utilized in a solid dissolvable form.

[0022] The flow rate at which the effluent passes through the individualbaffle chambers in the sedimentary deposit tank is an important featureof the solid removal system. Precisely, it is desirable to have as slowa flow rate of effluent as possible, to maximize the time for theparticles to separate from the effluent in the sedimentary deposit tank.The flow rate of effluent through the sedimentary deposit tank ispreferably maintained at a relatively constant value and may beregulated to this end. However, the flow rate may be changed if, forexample, the surge tank becomes backed up with effluent. A typicaldental office disposes of about one litre of suction effluent per chairper working day, but this quantity may be higher if a cuspidor drain isalso connected to the suction apparatus (which may be desirable in theinterest of preventing additional undesirable mercury-containingparticles from entering the ecosystem, although it is undesirable inthat it will typically require a larger-sized separation apparatus tohandle the larger volume of effluent). The optimal flow rate setting canbe estimated empirically as being equal to the total volume of effluentgenerated during a duty cycle (for example an 8 hour working day),divided by the total available time for operating the sedimentationsystem per duty cycle, the resulting rate multiplied by an appropriatesafety factor (greater than 1.0) to guard against backup of the systemto give the optimal flow rate. For this purpose, not only are theelements of the apparatus according to the invention suitably selectedfor dimensions, capacity, vacuum level, etc. (this may be doneempirically), but also a flow meter and needle valve or other suitableflow regulator may be installed to control the rate of outflow from thesedimentary deposit tank. The needle valve is adjustable to change theflow rate by changing the valve orifice size. The flow meter measuresthe flow rate of effluent exiting the sedimentary deposit tank anddisplays the flow rate measured, permitting the operator to adjust theflow by adjustment of the needle valve. While alternative automatic orsemi-automatic feedback control of the flow can be devised, it would beexpected to add appreciably to the cost of manufacture of the equipment.

[0023] Although the sedimentary deposit process is effective to remove asatisfactorily high proportion of the target particles desired to beremoved from the effluent, the sedimentary deposit tank desirablyincludes an outlet screen filter in the final baffle chamber to catchany floating materials as well as any other materials that did notsettle out in the upstream baffle chambers. Downstream of thesedimentary deposit tank, an auxiliary filtration unit to filter outfiner solids may be provided, and a mercury vapour filter may beprovided in the air bypass conduit. In the preferred embodiment of theinvention, the auxiliary filtration unit is incorporated into theconstruction of the sedimentary deposit tank and may be located in thefinal baffle chamber of the tank.

[0024] Desirably, at least the sedimentary deposit tank and optionallyvarious filtration units may be connected to the system as removablemodular units, or if the filtration unit is desired to be removedindependently of the sedimentary deposit tank, each of the sedimentarydeposit tank and filtration unit may be devised as removable modularunits. For heavier volume effluent processing, two or more sedimentarydeposit tanks may be coupled into the system in parallel or in series.It is expected that modular design will be most efficacious for dentaloffices because it is not to be expected that dentists or their staffwill be effectively able to remove deposited sediment from thesedimentary deposit tank nor remove accumulated particle residues fromthe filtration unit. It is desirable that such removal be done by acompetent effluent residue processing facility. Therefore, it isexpected to be preferred that the modular sedimentary deposit tankand/or filtration unit be removed periodically and replaced by freshsuch tanks or units from time to time as required. The spent tank orunit with an accumulation of metallic particles can then be sent to aprocessing facility for removal of the metallic particles, possiblychemical separation of mercury from silver, etc., and cleaning of themodular units for re-use. However, if, in any particular installation,it is desired instead that onsite removal of particles be effected, thensuitable bypass valves should be provided at the appropriate fluid flowports, and means provided for removal of particles (e.g. for thesedimentary deposit tank, the entire top wall might be opened orremoved, and for the filtration chamber, an access door provided topermit replacement of filters and removal of particles, etc., accordingto the designer's preference).

[0025] Further, according to another aspect of the invention, a fullsedimentation tank may be disconnected from active use, and connected toa suction attachment to transfer excess waste water from thesedimentation tank into the surge tank which waste water in turn isretreated in the replacement sedimentation tank. The full tank may thenbe coupled into a drying conduit connection for a period of time andexposed to tank-drying airflow to permit liquid in the tank to vaporizeand be removed in the air outflow. A dry tank is easier to handle bywaste processing service personnel than a tank containing a large volumeof liquid. Further yet, monitoring means may be provided to determinewhen the solids content of a sedimentary deposit tank has reached apredetermined level, so as to facilitate transfer of the effluent to apreviously idle sedimentary deposit tank.

[0026] For the apparatus to work to best advantage without dependence ongravity, a pressure differential must be maintained between the inletport of the surge tank and the outlet port of either the filtration unitor the outlet port of the sedimentary deposit tank if no filtration unitis present. To this end, the air pressure at the system outlet ismaintained at a level less than the air pressure at the system inlet.Assuming that the system operates by using a vacuum pump, the pressuresin question are below atmospheric pressure. The system requires that airenter the inlet either via the dental chair suction devices or via aseparate air inlet, preferably a vacuum break valve as described below.Consequently, in a vacuum system, the inlet pressure is nearer (butbelow) atmospheric pressure, while the downstream pressure at theseparator outlet is nearer the pressure drawn by the vacuum pump. Thispressure differential causes an overall flow of effluent fluid throughthe surge tank, into the sedimentary deposit tank, thence to theauxiliary filtration unit (if present), to exhaust via the separationsystem outlet into the vacuum pump exhaust line.

[0027] A vacuum pump may apply a partial vacuum at the system inletport, while at the system outlet port, the vacuum pump draws a highervacuum, so that there is a pressure differential sufficient to driveeffluent liquid properly through the separator system. A pressuredifferential of the order of 3-10 kPa between inlet and outlet vacuumlevels is sufficient to cause liquid effluent to flow through a smallsimple system, but depending upon the pressure drops within the system,the size of ports, passages, chambers, viscosity of the effluent, etc.,the pressure differential may have to be higher. It is best, again, totake an empirical approach and permit the pressure differential to beadjusted manually to suit the user's requirements.

[0028] In order to maintain constant air flow through the apparatus whenthe vacuum pump is operating, there is a spring-loaded vacuum breakvalve that opens when the suction apparatus openings from the dentalchairs are all closed. (Depending upon the spring force exerted on thevacuum break valve, the valve will remain closed when the suctionequipment of one or more dental chairs operates, and the requisite inputair to the system will be provided via the dental chair suctionapparatus.) When the vacuum break valve is opened, the top of the surgetank is open to the ambient air, and suction through the apparatus iseffected, causing fluid to flow through the apparatus.

[0029] The required air pressure differential between inlet and outletcan instead be positively applied by an air pressure source, but in thatevent, some means must be interposed at the surge tank to prevent airpressure from driving effluent upstream. According to an aspect of theinvention, an additional regulator valve for the surge tank may beprovided to accommodate a positive air pressure. The positive airpressure is applied during intervals between successive active operationof the suction drainage system from dental chairs. As dental officesinvariably have a source of air under pressure, this source may be usedto provide a positive air pressure differential.

[0030] If the surge tank becomes full, overflow effluent is suckedthrough the air outlet port and discharged into the air bypass conduit,thence to the vacuum pump draw line and thence eventually into themunicipal drain. However, it is desirable that the system should operatein such a manner as to avoid having the surge tank become completelyfull, since effluent exiting through the air outlet port will containparticles that will not be separated by the separator. Even if apinnacle filter or the like catches some of these particles, solutes andsome finer solid particles would be expected eventually to be dischargedinto the municipal drain. A user of the separator accordingly may wishto adjust the pressure differential of the vacuum system or the size ofa constriction in the outlet conduit for the separator, or otherwisesuitably adjust the flow rate through the system to prevent overflow.The users may also temporarily suspend discharge of large quantities ofliquid into the dental chair suction apparatus if the surge tank is onthe verge of becoming full.

[0031] It is accordingly preferable that one or more liquid levelsensors for sensing liquid level within the surge tank are provided thatwill cause suitable warning signals to be displayed or heard as theliquid level in the surge tank increases. For example, the sensingmechanism could sense when the surge tank is ¼full, ½full, ¾full, and⅞full, and at each threshold liquid level within the surge tank, couldprovide a suitable warning signal (perhaps using lamps of differentcolours to correspond to different threshold levels, etc.). Further,when the liquid level in the surge tank has reached (say) the ⅞level, itmay be desirable to alert the users of the system by a more urgentsignal (e.g. an audible signal) so that the users will be more urgentlywarned of the risk that the surge tank may soon be full.

[0032] It is also desirable to monitor solids levels in the sedimentarydeposit tank or tanks. Solids should preferably accumulate in such tanksonly to a fraction of the total tank volume so as not to interfereunacceptably with the settlement process within baffle chambers. Asbaffle chambers fill up with solids, liquid flow through the tank becomeimpeded or deflected and the tank becomes increasingly less effective topromote settling out of solids. In this specification, reference to a“full” sedimentary deposit tank that should be removed and replaced by afresh tank, or cleaned out, implies a tank filled with solids to theextent that the user of the system or its designer considers to beacceptable, but does not imply a tank totally filled with solid waste.

[0033] Monitoring of solids level within the sedimentary deposit tankmay be conveniently be accomplished by a sensor responsive to variationsin dielectric constant installed at an appropriate location on anexterior wall of the settlement tank—atop the lid or at the bottom ofthe sedimentary deposit tank, or preferably at a threshold levelposition along a side wall. Similar such dielectric-constant variablecapacitance-type sensors are commonly used as stud finders for locatingstuds in closed walls. The location of the sensor on an exterior sidewall of the settling tank, so that the sensor path is generallyhorizontal, may be more reliable in that the distinction between liquidand solids in the path of the sensor is more pronounced than the gradualchange in dielectric constant that would be sensed by a sensor atop thetank lid whose sensor path is vertical. In either case, the operatingprinciple is the same while the solids level in the tank is below thethreshold level established for warning detection by the dielectricsensor, no warning signal is supplied, but when the solids level risesto the threshold level above which the sensor provides a warning signalin response to the change in dielectric constant of the solids in thedetection path of the sensor, a suitable alert signal (audible, visual,or both as required) can then warn the user that the tank is adequatelyfull and should be removed and replaced, or cleaned.

[0034] Monitoring of flow activity within the sedimentary deposit tankmay be conveniently be accomplished by a sensor responsive to changes indielectric constant between effluent liquid and air installed at the topof the tank. When the dental office is working actively, the sedimentarydeposit tank quickly fills up and liquid rises to at least some extentin the surge tank. When the office shuts down for the day, effluentdrains out of the top of the tank to the extent permitted by the outflowconduit, leaving at least some empty space at the top of the tank. Ifthe dielectric liquid level sensor is installed in that space, thesensor will be responsive to the change in dielectric constant detectedwhen the liquid level in the tank falls below the sensor location. Achemical agent supply pump can be controlled by a suitable controlcircuit which is responsive to the dielectric liquid level sensoraccordingly supply precipitant or other chemical agents at a constantrate determined by the pump to the tank when it is operating, but toshut off when the liquid level in the tank falls below the sensorlocation. This of course may happen during slack times as well asovernight and on weekends, etc.

[0035] The particular sensing devices chosen for sensing liquid levelwithin the surge tank, the warning signal devices and the electricalmeans for actuating them can all be of conventional design and are notindividually per se part of the present invention.

[0036] While the invention using a vacuum system is operable if itsvacuum source or other source of pressure differential is not connectedto the vacuum source for the dental chair suction apparatus, it isconvenient and considerably less costly to use a single vacuum pump toserve both the dental chair suction apparatus and the separatorapparatus. While, as mentioned, positive air pressure may be usedinstead of an air pressure differential maintained by vacuum, the systemmay be somewhat less complex and less expensive to manufacture if avacuum system is used throughout, utilizing the vacuum pump alreadypresent in the dental office.

[0037] In a further embodiment of the invention oriented towardslarge-scale institutional applications in which many dental chairs orother sources of effluent are connected to the same suction and drainservices, several parallel-connected sedimentary deposit tanks andassociated apparatus, each such composite apparatus including a surgetank and preferably one, or alternatively two attached sedimentarydeposit tanks, may be operated in parallel to provide sufficienttreatment capacity for large effluent volumes. In such largeinstallations, fluid flow through the individual sedimentary deposittanks may be controlled by the flow gauge and needle valve meansdisclosed above, or may preferably be controlled by one or more separateauxiliary effluent vacuum pumps in order to reduce the complexity ofadjusting multiple needle valves (or similar individually adjustableflow control devices for each tank) to equalize effluent flow throughmultiple deposit tanks.

[0038] While the invention has been described in the context of a dentaloffice and is expected that dentists will be the primary users of theinvention, the invention has application to other similar effluentseparation situations. For example, with suitable changes to meetparticular situations, the invention may be adapted for use withjewellers' effluent, diamond cutting effluent, dental laboratorieseffluent, and the like. Where the effluent contains potentially valuablerecoverable solids, filters and other removal apparatus and proceduresshould be selected to maximize the recovery. Equally, for pollutioncontrol, recovery of environmental contaminants may be desirable.

SUMMARY OF THE DRAWINGS

[0039]FIG. 1 is a schematic isometric view of a preferred embodiment ofparticle removal apparatus according to the invention, for particularuse in a dental office.

[0040]FIG. 2 is a schematic section view of a vacuum break valve for usein the apparatus of FIG. 1.

[0041]FIG. 3 is a schematic isometric view of the sedimentary deposittank of FIG. 1 in exploded view illustrating the internal constructionof the sedimentary deposit tank, including baffle chamber walls,removable baffles and sedimentary deposit tank lid.

[0042]FIG. 4 is an isometric view of a multi-surface chevron-shapedbaffle unit according to the invention.

[0043]FIG. 5 is an isometric view of a multi-surface gable-shaped baffleunit according to the invention.

[0044]FIG. 6 is a schematic diagram of a dental office vacuum linecomprising dental chair suction apparatus openings, the apparatusaccording to the invention, a vacuum pump and drain.

[0045]FIG. 7 is a schematic isometric view of a portion of a preferredembodiment of particle removal apparatus according to the invention,showing the surge tank and an exemplary three sedimentary deposit tankscoupled together in series.

[0046]FIG. 8 is a schematic isometric view of a portion of a preferredembodiment of particle removal apparatus according to the invention,showing the surge tank and an exemplary three sedimentary deposit tankscoupled together in parallel.

[0047]FIG. 9 is a schematic isometric view of an alternative preferredembodiment of a surge tank according to the invention, for use with apositive air pressure system.

[0048]FIG. 10 is an isometric view of a preferred embodiment of anoutlet pipe structure for a sedimentary deposit tank, illustrating ananti-sludge protecting sleeve and needle valve.

[0049]FIG. 11 is an isometric view of a preferred embodiment of a largescale institutional application of the present invention, illustratingone separate auxiliary effluent pump located downstream of multiplesedimentary deposit tanks.

[0050]FIG. 12 is an isometric view of an alternative embodiment of alarge scale institutional application of the present invention,illustrating multiple separate auxiliary effluent pumps located upstreamof the multiple sedimentary deposit tanks.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

[0051] Separator apparatus 10 according to the preferred embodiment ofthe invention is shown generally in FIG. 1. The positioning of apparatus10 in combination with the conduits of conventional suction apparatus ina representative dental office is illustrated in FIG. 6. The separatorapparatus 10 is installed downstream of at least one suction apparatusopening 9 (sometimes referred to herein as an “operatory”) associatedwith a dental chair, and upstream of a vacuum pump 11. The suctionapparatus opening 9, apparatus 10, and vacuum pump 11 are interconnectedto form a vacuum line in which there is a continuous conduit for fluidto flow from each suction apparatus opening 9 to the vacuum pump 11.When operating, the vacuum pump 11 creates a pressure differential alongthe vacuum draw line 77 that is coupled to all vacuum lines upstream,thereby generating a suction force along a path from the vacuum pump 11through the apparatus 10 and to each suction apparatus opening 9.

[0052] Such effluent from the dental chairs and a quantity of air aresucked through a suction apparatus exhaust conduit 12, through a surgetank inlet pipestem 13 (FIG. 1), and thence into a surge tank inlet port14 of a surge tank 16. The air inflow required to maintain suction ismaintained either via the dental chair suction outlets 9, or if nodental chair suction line is operating, via vacuum break valve 22 atoppipestem 13, as will be described further below.

[0053] The mostly liquid effluent normally passes out of the surge tank16 via surge tank effluent outlet basin 18, while an air outlet port 20passes effluent air downstream via bypass conduit 26. An optionaldeflector (not shown) may be positioned at the top of and inside thesurge tank 16, between the surge tank inlet port 14 and the air outletport 20, and would extend downward within surge tank 16 to a selecteddepth, serving as a baffle to reduce the amount of liquid effluent thatis sucked into the air outlet port 20.

[0054] The surge tank effluent outlet port 18 passes effluent out of thesurge tank 16 and into sedimentary deposit tank 38 a and thence intofurther downstream portions of the apparatus 10 for target particleseparation and effluent discharge. A manually operated shut-off valve100 closes the surge tank outlet basin 18 when the tank 38 a is to beremoved for cleaning or replacement. When the vacuum pump 11 isoperating, the air pressure differential between the surge tank inletport 14 and downstream outlet conduit 77 leading into vacuum pump 11(see FIG. 6), forces effluent, and some air, out of the surge tank 16and into the sedimentary deposit tank 38.

[0055] A vacuum at the air outlet port 20 is generated when the vacuumpump 11 is operating, thereby sucking air out of the surge tank 16, tobe discharged from the apparatus 10 via common outlet conduit 77 intowhich bypass line 26 feeds. Matter sucked by the vacuum pump 11,generally free of removed solids as will be described further below, isdischarged via vacuum pump exhaust line 17 into a municipal drain of thepublic sewage system 15. Such effluent matter typically includes amalgamparticles and solutes, aluminum oxides used in air abrasion treatment,enamel and dentine from teeth, porcelain, acrylic used in bridges,prosthetic cementing agents such as zinc phosphate cement used in crownsand bridges, and other solid material.

[0056] Typically, a pressure differential of the order of 3-10 kPabetween the inlet and outlet of the apparatus 10 is sufficient to causeliquid effluent to flow through the system if it is relatively small.However, the pressure differential may have to be higher depending uponthe pressure drops within the system, the size of ports, passages,chambers, etc. and the number of dental chairs served. Preferably, anempirical calculation is made and the pressure differential is adjustedmanually to suit the user's requirements, although an automatic feedbacksystem could be provided, if desired, to maintain output flow ratewithin a selected range of values.

[0057] Referring to FIGS. 1 and 2, the pipestem 13 terminates at itsdistal end in a vacuum break valve 22 opening pipestem 13 and thus surgetank 16 to the ambient air via ports 27 when the valve 22 is open. Thevalve 22 is biased closed by a spring 28 or other biasing mechanism andis shown closed (seated) in FIG. 2. Preferably, the valve 22 is aconventional air check valve, such as one of the KBI-CV series of checkvalves manufactured by King Brothers Industries (Valencia, Calif.). Innormal operation, a suction force effective at the surge tank air outletport 20 draws air into the air bypass line 26, while the suction forceeffective at outlet basin 18 draws effluent liquid into the surge tank16 from line 12. When the dental office suction apparatus openings 9(FIG. 6) are closed and consequently suction apparatus line 12 isclosed, the pressure inside the surge tank 16 drops as a result of thevacuum caused by the vacuum pump 11, and the increased pressure dropovercomes the biasing force of the spring 28, causing the vacuum breakvalve 22 to open, permitting replacement air to enter the surge tank 16and both the airflow and liquid effluent flow to be maintained throughthe system. When the suction apparatus openings 9 are reopened, airentering into the surge tank 16 through the surge tank inlet port 14neutralizes the pressure differential at the vacuum break valve 22,permitting the spring 28 to re-close the vacuum break valve 22. Thepressure drop at which valve 22 opens can be adjusted by varying theselected compression and stiffness of the spring 28.

[0058] The level sensor port 24 shown atop surge tank 16 in FIG. 1receives a level sensor probe 30 inserted therethrough and sealed intothe sensor port 24, only the upper portion of which probe 30 appears inFIG. 1. Preferably, the probe 30 is a conventional fluid level detectionsensor responsive to changes in dielectric constant between effluentfluid and air and having a plurality of sensing means, each sensingmeans connected to an associated wire pair among the wire pairs of alevel signal cable 25, the sensing means being vertically spaced fromone another within the surge tank 16. When the liquid level within surgetank 16 reaches any particular sensing means, the sensor is responsiveto the change in dielectric constant between the air and the effluentfluid in the surge tank 16, and transmits a signal along the wire pairattached to the sensor. The associated wire pairs of cable 25 connectthe liquid level sensors to warning display unit 32. The display unit 32comprises one or more audible alert devices 34 and a series of visualalert devices 35 that are responsive to the data level signals so as toprovide alert or warning signals indicating the level of effluent withinthe surge tank 16. In a preferred embodiment, the probe 30 responds toliquid levels within the surge tank 16 at the ¼full, ½full, ¾full and⅞full values, and at each such liquid level, the display unit 32provides a suitable warning signal using, for example, lamps ofdifferent colours to correspond to different liquid levels. Further,when the liquid level in the surge tank 16 has reached the ⅞level, theuser is alerted by a more urgent signal (e.g. an audible signal) warningof the risk that the surge tank 16 may soon be full. The user may inresponse to such warning increase the flow rate out of sedimentarydeposit tank 38, or reduce the incidence of use of the dental chairsuction drains 9, or take other remedial measures. In an alternativeembodiment, the liquid level sensor means may be mounted externally onthe sides of the surge tank 16 located at appropriate levels to indicatewhen the tank is ¼full, ½full, ¾full and ⅞full, for example.

[0059] If effluent is deposited into the surge tank 16 when the surgetank 16 is full, excess effluent is sucked through the air outlet port20 and is pulled by vacuum pump 11 along liquid bypass conduit 120running in parallel with the air bypass conduit 26 and discharged fromthe apparatus 10 into the municipal drain (thereby preventing effluentfrom backing up through the pipestem 13, suction apparatus exhaustconduit 12, and eventually the suction apparatus openings 9).Preferably, no effluent is deposited into the suction apparatus openings9 when the surge tank 16 is full, as target particles in the effluentdischarged through the air bypass conduit 26 will not be separated fromthe effluent by sedimentary deposit tank 38. As a precaution in theevent that passage of liquid effluent containing solid particles throughthe bypass conduit 26 does occur, pinnacle filter 89 (FIG. 1) isintended to catch at least the larger target particles that are presentin such effluent, thereby tending to avoid damage to the vacuum pump 11and to afford an “insurance” opportunity to remove unwanted particlesbefore they pass into the municipal system. However, it is best to avoidoperation of the system that results in any passage of liquid throughbypass conduit 26.

[0060] Referring to FIGS. 1 and 3, effluent from surge tank outlet basin18 passes through a sedimentary deposit tank inletport/pipestem/coupling 36 a and into sedimentary deposit tank 38 a. Thesedimentary deposit tank 38 a is provided with a plurality of bafflechambers 42, 44, 46, 48, 50, 52, one or more precipitant inlet ports 53sealed to the top of sedimentary deposit tank 38, and a deposit tankoutlet conduit/pipestem 55 a.

[0061] As shown in FIG. 3, the baffle chambers 42, 44, 46, 48, 50, 52are bounded by transverse baffle chamber boundary walls 54. Each bafflechamber wall 54 is arranged vertically and parallel to the other bafflechamber walls 54. Each baffle chamber wall 54 has a wall opening 56 inthe form of a rectangular notch located near the top edge of the bafflewall 54. The wall openings 56 alternate in transverse position so as tomaximize the effluent travel distance from one wall opening 56 to thenext. The side and bottom edges of each baffle chamber wall 54 areconnected to the interior surfaces of the sedimentary deposit tank 38 ato form a fluid-tight seal so that effluent can flow from one bafflechamber to an adjacent baffle chamber only through the common bafflechamber wall opening 56. In a preferred embodiment of the sedimentarydeposit tank 38 a the baffle chamber walls 54 are formed as integralparts of the tank unit. Altenatively, in a further embodiment of thesedimentary deposit tank 38 a, the baffle chamber walls 54 may be formedseparately from the tank 38 a and may be removably inserted into matingslots located on the walls and bottom of the deposit tank 38 a to dividethe tank into separate baffle chambers.

[0062] In the preferred embodiment, the baffle chambers comprise, indownstream order: an inlet baffle chamber 42, a second baffle chamber44, a third baffle chamber 46, a fourth baffle chamber 48, a fifthbaffle chamber 50, and an outlet baffle chamber 52, although the numberand size of baffle chambers is within the designer's discretion.

[0063] Referring to FIGS. 3, 4, and 5, the inlet, second, third, fourthand fifth baffle chambers 42, 44, 46, 48, 50 comprise inclined (eitherin one dimension or two dimensions) baffle units 67, 68 selectivelyarranged within each baffle chamber 42, 44, 46, 48, 50, 52 so that eachbaffle unit 67, 68 directs the fluid flow but does not interrupt it. Ina preferred embodiment of the invention, the baffle units 67, 68 may beeither chevron-shaped elements 67 as shown in FIG. 4 or gable shapedelements 68 as shown in FIG. 5, depending on the needs of the user andthe characteristics of the effluent to be treated. In an alternativeembodiment, the baffle surfaces may be simply inclined planar surfaces,similar to those disclosed in the applicant's previously published PCTInternational Patent Application No. PCT/CA99/00665 filed on Jul. 21,1999, from which this application claims priority. Referring to FIG. 3,liquid passes from inlet baffle chamber 42 to the second baffle chamber44 via port 56, from the second baffle chamber 44 via a second port 56to the third baffle chamber 46, and thence to the fourth baffle chamber48 via a third port 56. Preferably, the surfaces of the baffle units 67,68 lie at a angle of about 60°to the deposit tank floor 69, and in thecase of the gable-shaped baffle units 68 angled in two dimensions, asecondary angle of about 30°to the baffle chamber walls (54) so as tooptimize convection of the effluent through the baffle chambers andparticle separation. The user may wish to consult published experimentalstudies of preferred inclined sedimentation techniques, such asImportance of Convection to the Enhancement of Erythrocyte SedimentationRates in Inclined Tubes, Hocking et al. (Biorheology, 24; 473-482,1987). Hocking shows that the rate of settling of erythrocyte particlesfrom liquid whole blood onto a surface increases as the angle of thesurface is increased, reaching a maximum settling rate when the surfaceis 60°from the horizontal plane, and that selective placement of thesurfaces encourages advantageous fluid flow patterns for increasedparticle separation.

[0064] In a preferred embodiment of the invention designed to minimizemanufacturing costs associated with producing baffles, chevron orgable-shaped baffles 130, 135 are formed individually with attachedflanges or ribs 132, 136 to provide for separation of multiple baffleswhen stacked in a baffle chamber. In the case of chevron-shaped baffles130, such separation ribs 132 are located near the outer edges of thebaffle, and may be oriented parallel to effluent flow as illustrated inFIG. 4, or alternatively, perpendicular to effluent flow, similar toribs 135 shown in FIG. 5. Such separation ribs 132 may also be locatedalong the baffle centerline, and may be rectangular or cylindrical incross section. In the case of gable-shaped baffles 135, such separationribs 136 are located near the outside edges of the baffle, and near thecentral apex of the baffle, and may be oriented parallel orperpendicular to effluent flow similar to ribs 132 and 136 in FIGS. 4and 5, or may alternately be located along the baffle centerline, andmay be rectangular or cylindrical in cross section. In a furtherpreferred embodiment designed to minimize the cost of assemblingsedimentary deposit tank equipment, two or more baffles 130, 135 may beformed together as a single integrated baffle unit 67, 68 includingspacing ribs 132, 136 to align and separate the baffles as discussedabove. In such an embodiment, for applications where gable-shapedbaffles 135 are used, three gable baffles 135 are preferably formedtogether in a vertically stacked configuration to form a singlegable-shaped baffle unit 68. In applications where chevron-shapedbaffles 130 are used, it is preferable to form two chevron baffles 130together in a vertically stacked configuration to form a singlechevron-shaped baffle unit 67. It is desirable to utilize variations inthe number and separation (i.e. relative spacing) of baffles used in abaffle chamber (either as individually formed and stacked baffles or asjointly formed baffle units) in order to customize the arrangement ofbaffles inside the sedimentary deposit tank 38 a, depending on thecharacteristics of the effluent to be treated. For example, in anapplication where the effluent to be treated is expected to contain asignificant portion of very small particles, in addition to largerparticles, it may be advantageous to utilize a greater number of baffleswith smaller spacing therebetween in the downstream baffle chambers ofthe sedimentary deposit tank 38 a, in order to increase thesedimentation of smaller particles after the larger particles havesettled out in the upstream baffle chambers. It is expected that suchvariations in baffle configuration are best determined empirically, asthey are dependent on factors such as effluent characteristics, whichmay vary significantly between applications.

[0065] Baffle chamber 42 is configured slightly differently from theother baffle chambers in order to accommodate the inlet pipestem 36 a.Baffle chambers 44, 46 and 48 may be essentially identical, but theinterior arrangement of the chambers and the respective size of thechambers is at the discretion of the designer.

[0066] Effluent passing into the sedimentary deposit tank 38 a throughthe deposit tank inlet port 36 a first collects in the inlet bafflechamber 42. As time elapses, metal particles and other solid particlesheavier than the liquid effluent separate from the effluent and settleon the surface of a baffle unit 67 or 68 or on the sedimentary deposittank floor 69; the more time that elapses, the greater the amount ofgravity-induced particle separation. To separate solute metal particlesdissolved in the liquid effluent, a chemical agent such as aprecipitant, chelating agent, or flocculant may be controllablydelivered via one or more inlet port(s) 53 by one or more deliverypump(s) 23 fed by one or more supply vessel(s) 70 and injecting chemicalagent via supply conduit 29 sealed into port 53. Preferred chemicalagents for dental office use include precipitants potassium iodide (KI)or sodium borohydrate (NaBH₄) mixed with sodium hydroxide (NaOH) orsodium sulfide (Na₂S), the latter combination however having a sulfurousodour, and the chelating agent EDTA, however any precipitant orchelating agent suitable for combining with solute mercury or silver orboth, may be selected. Supplied in 1-molar concentrations, thesechemical agents may be added to the effluent in the ratio of about 2parts per 1000. Strong oxidizing or reducing agents should not be usedin significant concentrations, as they may release mercury fromparticulate amalgams. Addition of a flocculant to a precipitant orchelating agent may promote further particle separation from theeffluent; fungicides and antibacterial agents may also be contained inthe supply vessel 70. The flocculent, if present, combines with metalparticles and causes such particles to combine into larger masses, sothat metal particle separation is further promoted. Suitable flocculantsinclude aluminium sulfate and aluminium chloride. Anti-fungal agentsinclude acridine dyes and anadine dyes.

[0067] The pump 23 may operate at a constant speed, delivering aconstant flow of chemical agent into the tank 38 a while operating.However, the pump 23 should not operate when the dental office is idleduring slack times, overnight or during weekends, etc. To this end, thepump 23 operates under the control of a liquid level sensing probe 117located at the top of tank 38 a, or preferably, attached to the side ofthe tank 38 a, near the top thereof. The probe 117 may comprise a sensorresponsive to changes in dielectric constant of the same general sort asdescribed previously with reference to level sensing probe 30. Duringidle hours, liquid in the surge tank 16 will drain into the tank 38, andeventually the level in the tank 38 a will fall to a rest leveldetermined by the height of the orifices 56. The sensing means of probe117 should be positioned so that the sensing means detects the change indielectric constant between the effluent and air and transmits a signalto a suitable control circuit just before the liquid level in tank 38 areaches rest level. The pump 23 is controlled by the control circuit tooperate when the sensing means reports the dielectric constant of theeffluent, indicating that the liquid level in tank 38 a is above therest level and the system is in operation.

[0068] Alternatively, the chemical agent delivery apparatus 70 couldrespond to a time clock to deliver a selected amount of chemical agentper selected time interval (with a selection of zero for idle hours). Ina more complex arrangement, the delivery apparatus 70 could respond inpart to the flow rate of effluent passing out of tank 38 a as determinedby the setting of needle valve 85. The amount of chemical agent selectedto be applied per time interval or per unit of effluent flow will bedependent in part on the chemical characteristics of the agent selected,and in part upon the expected concentration of particles in theeffluent, and is usually best determined empirically.

[0069] Located at the fifth baffle chamber 50 and outlet baffle chamber52 are modular filtration or adsorption inserts 65, 66 which may beadapted to include a range of physical and chemical characteristics,depending on the needs of the system user and the characteristics of theeffluent to be treated. Such modular inserts are constructed to alloweasy removal and replacement within the sedimentary deposit tank 38 afollowing saturation of filter or absorbent material with particulate orother waste matter. In a preferred embodiment, one of the modular units65, 66 may be adapted to include an outlet baffle chamber filterpositioned so that effluent passing through the outlet baffle chamber 52and through the deposit tank outlet pipestem/port/coupling 55 a mustfirst pass through the baffle chamber filter. The filter can be of finemesh or fibrous mat or the like within a constraining cage. Preferably,the filter is made from polystyrene or polyethylene or anotherbiologically inactive material so that microbes cannot utilize thefilter material for nutrients. The filter tends to catch any floatingsolid matter as well as any coarser solid matter that has not settledout in the upstream baffle chambers. Preferably, any precipitants,flocculants or other chemical agents used should not generate anabundance of floating solid matter, because otherwise the filter couldbe quickly clogged. If necessary, the size of the filter and of thefinal two baffle chambers 50, 52 can be increased if a high proportionof floating matter is expected to be entrapped.

[0070] In a further preferred embodiment, one of the modular units 65,66 may be adapted to include absorbent material used to adsorb dissolvedmercury or other metal ions from effluent solution. A preferredadsorbent material is finely divided bentonite clay particles, combinedwith activated silica particles to form granular pellets, which may beenclosed in a porous and permeable membrane, similar in function andappearance to a tea bag. Concentrated chlorine solution may also beadded to the effluent directly upstream of such an adsorbent modularunit through an appropriately located injector port 53. Suchconcentrated chlorine solution is effective to release metal ions fromdissolved organic compounds to facilitate more efficient adsorption bythe bentonite clay particles in the adsorbent modular unit, while theactivated silica particles in the modular unit are effective to adsorbsuch dissolved organic compounds. In another preferred embodiment, oneof the modular units 65, 66 may be adapted to include an auxiliary fineparticulate filter, which is effective to remove residual fineparticulate matter that has not settled out of suspension in theupstream baffle chambers 42, 44, 46, 48 of the sedimentary deposit tank38 a. A possible construction of the auxiliary filter is detailed belowin the description of an alternative external embodiment of the filter.

[0071] In the alternative embodiment of the auxiliary fine particulatefilter shown in FIG. 1, effluent passing out of tank outlet pipestem 55a next passes into the auxiliary filtration unit 74 located external toand downstream of the sedimentary deposit tank 38 a for a finalseparation of fine particles. Preferably, the filter is an inorganicpolymer filter for separating aqueous mercury from liquid. An example ofsuch filter is disclosed in Pierce et al. Chemically designedinorganically polymer filters for aqueous mercury separation, (Journalof Dental Research v.44, p.404, 1997) Alternatively, the filter offiltration unit 74 can be a conventional dual gradient cartridge filter.Additionally mesh filters or porous membranes may also be employeddepending upon available pressure differentials, flow-rate targets, andsize of particulate desired to be removed. The outlet of filtration unit74 is connected via outlet conduit 82 and thence via needle valve 85 tothe common exit conduit 77. The filtration unit 74 is preferablyattached to the deposit tank 38 a using quick release connectors toenable easy replacement of the modular filtration unit 74 as required.

[0072] In a preferred embodiment of the invention that includes a fineparticulate filter 74 in a modular unit 66 of the sedimentary deposittank 38 a, the outlet pipestem 55 a of the tank includes protectivesleeve assembly 144 to prevent clogging of the needle flow rate controlvalve 85 caused by floating particulate matter and froth or sludge whichcan accumulate around the exit port 55 of the tank. Such protectivesleeve assembly comprises a downwardly depending inner needle valveintake pipe 142 over which is fitted a downwardly depending protectivesleeve 144, which extends below the lower extremity of the inner intakepipe 142 by a margin of comfort to protect against the entrance offloating particulate matter or sludge into the intake pipe 142. Theprotective sleeve 144 is perforated by several radially spaced air holes146 located near the top of the sedimentary deposit tank 38 a such thateffluent is drawn into the intake pipe 142 only when the fluid level inthe tank is higher than the level of the lower end of the intake pipe142. If the fluid level in the tank 38 a drops below the level of thelower end of the intake pipe, air entering the air holes 146 in theprotective sleeve 144 will be drawn out of the tank through the needlevalve intake pipe 142 in place of effluent.

[0073] A disinfectant is added to the effluent at the individualoperatory suction openings 9 to control bacterial growth and odours inthe effluent treatment system. The addition of disinfectant additionallyserves to break down organic particles in the effluent, releasingcomplexed forms of mercury and other metals, which can then be removedfrom solution in the settlement tank 38 through the use of chemicalagents or adsorbent compounds. Preferred disinfectants are chlorine,bromine, or peroxide based, and utilized in a solid dissolvable brickform which is held in place at the individual suction openings 9 by aholding screen located in or near the opening 9 in the vacuum line.

[0074] It should be noted that depending on the choice of chemicalagents (precipitant, flocculant, chelating agent, disinfectant andadsorbent) selected for use in the treatment system, there exists apossibility for disadvantageous chemical interactions to occur, reducingthe effectiveness of one or more of the agents in use. Such chemicalinteractions may also be affected by the composition of the effluentbeing treated in the system. Therefore, an optimum combination ofchemical agents for use in treatment of a specific effluent stream maybe determined by empirical means.

[0075] Note that the flow rate of effluent through tank 38 a must be lowenough that target particles have adequate opportunity to settle out. Ina typical dental office using a vacuum pump 11, drawing a vacuum ofabout 25-50 kPa, a vacuum differential pressure between inlet port 14and outlet conduit 82 of about 3-10 kPa should be sufficient toestablish a suitable flow rate through tank 38 a, assuming a maximumeffluent volume of about 5 to 10 litres between inlet port 14 and outletconduit 82. Flow rate may be adjusted by means of a needle valve 85 intank outlet line 76 coupled downstream of the outlet pipestem 55 a atopthe tank 38 a and connected to the final baffle chamber 52; a flowmeter87 permits the operator to read the current flow rate and to adjust itas required using the needle valve 85. The flow rate should be set to anempirically estimated optimal rate equal to the total expected effluentvolume during a duty cycle divided by the total available time foroperating the sedimentation system per duty cycle, and multiplied by anappropriate safety factor (greater than 1.0) to guard against systembackup or overflow. For example, if an average dental chair producesabout 1 litre of effluent per duty cycle (working day), and there are 8dental chairs in the office served by the apparatus 10 which operatesover the 8 hour working day, a needle valve flow rate setting of about1.2 L/hr (20 mL/min) would accommodate all 8 chairs and provide a fairlysteady rate of flow through the sedimentary deposit tank 38 throughoutthe duty cycle, incorporating a safety factor of 1.2 to guard againstsystem backup. These devices 85, 87 are preferably positioned in theseparation system downstream of any removable modular devices such asthe tank 38 a and any auxiliary filter 74 present, and upstream of thejunction of the tank exit conduit 79 leading from tank 38 a and thecommon exit conduit 77.

[0076] It is desirable to utilize the minimum possible flow rate ofeffluent through the separation system to maximize the time for theparticles to separate from the effluent. However, the flow rate may bechanged if, for example, the surge tank 16 becomes backed up witheffluent. The volume of effluent per dental chair per day may varyoffice by office and pursuant to national preferences, regulations, etc.The use of cuspidors, ultrasonic scalers and other optional dentaloffice equipment may increase the volume of effluent produced. Theoptimal effluent flow rate through the sedimentary deposit tank 38 a canbe estimated empirically as outlined above such that the total effluentvolume generated during a duty cycle passes through the system as slowlyas possible without overflowing the surge tank 16. The flow rate throughthe apparatus 10 may be further controlled (in addition to by adjustingthe needle valve 85) by adjusting the suction force of the vacuum pump11.

[0077] There is a tendency of particles to settle out in the upstreambaffle chambers rather than the downstream baffle chambers within tank38. So the upstream chambers tend to fill up and clog the undersides ofthe baffles 67, 68 before the downstream chambers become very full ofsolid matter. A balance must be struck between maintaining optimaloperation of the baffles, on the one hand, and avoiding undue frequencyof cleaning or replacement of tanks 38, on the other hand. The usershould choose empirically how full a tank 38 a must be before it iscleaned out or replaced by a fresh empty tank. To this end, a solidslevel sensor 116 may be provided to indicate the level of depositedsolids in, say, the third or fourth baffle chamber of the tank.Dielectric constant sensor technology similar to that commonly used in“stud sensor” units may be used for such a solids level sensor, wherethe sensor 116 is responsive to the change in dielectric constantbetween effluent liquid in tank 38 a and deposited solids. When thelevel of solids rises to the level of the sensor, the sensor detects thechange in dielectric constant, transmitting a signal to an appropriatecontrol circuit located in display box 32 via signal cable 45. When thathappens, the control circuit in display box 32 provides a warning (bywarning lamp or the like) that the tank 38 a is full and should becleaned out or replaced by a fresh empty tank. While FIG. 1 shows analternative embodiment of the invention wherein the solids level sensor116 is mounted to the top of the sedimentary deposit tank and protrudestherein, in a preferred embodiment of the invention, such sensor 116 maybe mounted on the outside of the side wall of the third or fourth bafflechamber of the tank at a threshold level selected by the user.

[0078] Periodically, it is desirable to remove the metal particlescollected in the sedimentary deposit tank 38 a and filtration unit 74.According to the preferred embodiment, the sedimentary deposit tank 38 aand associated integrally constructed auxiliary modular filtration units65, 66 are removably connected to the apparatus 10 as readilycoupled/decoupled modular units. To this end, all conduit or portcouplings and all electrical connections should be of the quick-releasetype. The tank 38 a and other modular units can be removed from theapparatus 10 for metal particle recovery and cleaning, for example, at ametal particle recovery facility.

[0079] The air bypass vacuum line 26 is coupled to the surge tank 16 viaa bypass coupling collar 88 that is adapted to removably connect thevacuum line to the air outlet port 20, and the base of pipestem 13 alsopreferably includes a release coupling so that the surge tank 16 may bedecoupled for cleaning.

[0080] Bypass conduit 84 including shut-off valve 86 connects the surgetank pipestem 13 to the air bypass line 26. The bypass valve 86 isnormally closed when the surge tank 16 and sedimentary deposit tank 38 aare connected to the apparatus 10, but is opened when the tank 38 a isremoved. When the sedimentary deposit tank 38 a is removed, valve 100leading from exit basin 18 is closed. Eventually the surge tank 16 maybecome full of effluent. Air then passes through the suction apparatusexhaust conduit 12, through the upper portion of pipestem 13, throughthe by-pass conduit 84, and into the air bypass conduit 26, fordischarge into the vacuum draw line 77 and thence into the municipaldrain. When eventually liquid effluent passes from a full surge tank 16out of outlet port 20, the liquid passes through liquid bypass conduit120 running in parallel with the air bypass conduit 26, and eventuallyjoins common exit conduit 77 upstream of pinnacle filter 89. Thistemporary vacuum circuit enables the dental office suction apparatus tokeep functioning, albeit without as much solids removal as would occurif tank 38 a were connected, but with some solids removal by means ofpinnacle filter 89.

[0081] To avoid temporary problems associated with removal andreplacement or cleaning of sedimentary deposit tank 38, it is desirableto use two or more modular sedimentary deposit tanks operating inparallel or series. FIG. 7 illustrates an exemplary series connection ofthree sedimentary deposit tanks 38 a, 38 c, 38 d, and FIG. 8 illustratesan exemplary parallel connection of three sedimentary deposit tanks 38a, 38 e, 38 f. Each such sedimentary deposit tank would be provided withits own solids level indicator so that each upon being considered “full”would be removed and replaced. The use of two or more sedimentarydeposit tanks in series extends the flow distance for the effluent topass through the apparatus 10 compared to that for a single sedimentarydeposit tank. Therefore, greater separation of particles may be achievedfor a given flow rate, or a higher flow rate may be applied through theapparatus 10.

[0082] If a positive air pressure source instead of a vacuum source isconnected to provide the requisite pressure differential between theinlet port of the surge tank 16 and the exit conduit 77, or if thevacuum pump 11 may be operating only intermittently, a modified versionof the plumbing atop the surge tank 16 as shown in FIG. 9 isappropriate. (In Europe, it is common for the vacuum pump 11 to turn offwhen not in active use; in North America, the vacuum pump 11 tends torun constantly, at least during office hours.) Valves 118 and 119,interposed between the surge tank 16 and conduits 12 and 26respectively, are normally open when the dental office drains areoperating, in which case the positive upstream air pressure in line 12drives effluent downstream through the surge tank 16 and sedimentarydeposit tank 38, and drives air downstream through air bypass conduit26. When the dental office drains are not operating, in which case noupstream air pressure is applied, both valves 118, 119 close. In suchlatter instance, an air inlet port 112 located in the upper part of thesurge tank 16 opens, applying a modest air pressure to the interior ofthe surge tank 16 to compensate for the lack of air pressure in conduit12. Valve 118 can be a check valve that, like valve 22, operates inresponse to pressure changes. Valve 119 and the air pressure supply toair inlet port 112 may be solenoid actuated in response to interruptionin the supply of air pressure to conduit 12. The supply of air to airinlet port 112 is also preferably responsive to liquid level sensorprobe 117 or the equivalent, so that positive air pressure is no longerapplied once the liquid level in tank 38 a has dropped below thethreshold level determined by the probe 117 or the like.

[0083] In some working environments, the apparatus described above whoseprimary use is for solids removal may be provided with auxiliaryconduits for removing excess effluent from a full sedimentary deposittank that has been replaced, and drying the tank. Such full tankcontains mostly liquid and some solid. Assuming that the full tank is tobe taken off premises for solids removal and waste recovery andcleaning, the tank is more easily handled if it is not full of liquidbut is relatively dry. To this end, an attachment conduit 125 fittedwith a valve 126 is connected to the inlet port of the surge tank 16 andis also connected to the outlet port 55 b of the full sedimentarydeposit tank to be dried. By tilting the full tank, and opening thevalve on the attachment conduit, the excess liquid effluent can beremoved from the full tank under suction, returning the effluent to thesurge tank 16 and flow therefrom for retreatment in the newly installedempty sedimentary deposit tank. Following removal of excess liquideffluent from the full tank, auxiliary tank drying conduits 92, 93 mayeach be coupled at one end to bypass conduit 26 and at the other endrespectively coupled to pipestem couplings 36 b. 55 b respectively of atank 38 b to be dried, as illustrated in FIG. 1. A shut-off valve 114 isinterposed in line 26 between the points of connection of conduits 92,93 with the line 26. Shut-off valves 115, 113 respectively are providedfor the conduits 92, 93. When tank 38 b is to be dried, valves 115, 113are open and valve 114 is closed, forcing the air entering line 26 topass through conduits 92, 93 and therefore the interior of tank 38 b,thereby permitting the flowing air to remove water vapour from the tank38 b. When the dried tank 38 b is to be removed and another tank put inits place, or whenever the drying option is not to be used, valves 115,113 are closed and valve 114 is open, directing the air along conduit 26without passing through conduits 92, 93.

[0084] As the air entering the conduit 26 is invariably humid, thedrying option described above 4may not work well in all situations. Aheater (not shown) could be provided to warm the air before it enterstank 38 b, but that increases the expense of manufacture and theoperating expense. An auxiliary tank drying apparatus separate from theeffluent treatment apparatus would be more economical in somesituations.

[0085] Mercury vapour may remain in the air line; it will not beentrapped by the sedimentary deposit tank 38 a nor by filters downstreamthereof because the vapour preferentially passes through bypass conduit26. A mercury vapour trap or filter 101 may be provided in the conduit26 to remove at least some mercury from the effluent air. A suitablemercury vapour filter is described in Boliden U.S. Pat. No. 5,205,743issued Apr. 27, 1993; selenium is a suitable material for use in suchfilters. Activated charcoal impregnated with various active mercurybonding agents may also be used. Note that the mercury vapour trap willalso catch such vapour emanating from the tank 38 b being dried.

[0086] Note that the provision of liquid effluent bypass conduit 120located beneath air bypass conduit 26 permits excess liquid to flow fromsurge tank 16 to common exit conduit 77 without interfering with airflow through the drying conduits 92, 93 and without interfering with theoperation of the mercury vapour filter 101. The bypass line 120 shouldjoin conduit 77 upstream of pinnacle filter 89 so as to remove at leastcoarser solids in the event of such overflow from surge tank 16.

[0087] An alterative embodiment of the present invention is orientedtowards institutional or other large-scale use where many dental chairsor other sources of effluent are connected to the same suction andeffluent discharge services, such that the volume of effluent generatedduring a duty cycle exceeds the capacity of a single settlement tank 38.In one such large scale installation, the effluent travels through twoor more settlement systems arranged in parallel, each settlement systemcomposed of a surge tank 16 connected to preferably one, butalternatively two settlement tanks 38. The common main vacuum line 12connects to two or more surge tanks 16 a, 16 b through one or moreT-junction connectors. Similarly, the treated effluent exiting thesettlement tanks 38 through the tank exit conduits 79 are connected to acommon main exit conduit 77. The pressure differential required to movethe effluent through the parallel settlement systems can be provided bythe common system vacuum pump 11 as in the small dental officeinstallation described above, or by a separate auxiliary effluent pump160.

[0088] The use of a separate effluent pump 160 allows the settlementsystem to operate 24 hours per day, independent of the operation of thesystem vacuum pump 11. This allows the reduction of the minimum possibleeffluent flow rate by lengthening the settlement time to processeffluent from one duty cycle, optimizing sedimentation. Therefore, theoptimum effluent flow rate becomes the total volume of effluentgenerated in one duty cycle (an 8 hour working day) divided by the totalavailable time for operation of the system per duty cycle (24 hours dueto continuous operation of effluent pump 160), multiplied by anappropriate safety factor to guard against system backup. Additionally,a separate effluent pump 160 also eliminates the need to individuallycalibrate vacuum needle valves 85 on each settlement tank 38 in order toensure equal effluent flow through each tank 38 installed in parallel.Instead, in an installation where a separate effluent pump 160 isutilized, the main system vacuum pump 11 is connected only to the surgetanks 16, but not also to the individual settlement tanks 38 as in thesmall dental office installation. In addition, when a separate effluentpump 160 is used, the treated effluent leaving the settlement tanksthrough tank exit conduits 79 flow into a common effluent drain 162which is separate from the main vacuum exit conduit 77.

[0089] As shown in the preferred embodiment of a large institutionalinstallation in FIG. 11, the separate effluent pump 160 is preferablylocated downstream of the settlement tanks 38 g, 38 h in order to reducewear on the pump caused by abrasion from amalgam and other particlessuspended in the effluent before sedimentation, and to reduce thedissolution of mercury into the effluent caused by the turbulence insidethe effluent pump 160. In an alternative embodiment shown in FIG. 12,multiple separate effluent pumps 160 a, 160 b can be located upstream ofthe settlement tanks 38 g, 38 h between the individual surge tanks 16 a,16 b and the settlement tanks 38 g, 38 h to force effluent through thetanks by positive pressure. The schematic representations of the largeinstitutional installations shown in FIGS. 11 and 12 omit many of thedetailed elements of the treatment system for the sake of clarity,however, it is expected that the additional system elements as shown inFIGS. 1, 2 and 9 and described in the foregoing will remain part of suchinstitutional installations including such elements as fluid and solidlevel sensors and control systems, conduits and flow control valves,chemical agent injection ports and supply pumps, pinnacle filters,auxiliary effluent suction conduits, and the like.

[0090] Other alternatives and variants of the above described methodsand apparatus suitable for practising the methods will occur to thoseskilled in the technology. The scope of the invention is as defined inthe following claims.

What is claimed is:
 1. Apparatus for separating metallic particles fromliquid effluent flowing from a source thereof, including optionally oneor more surge tanks for collecting a quantity of effluent containingsuch metallic particles; and one or more sedimentary deposit tanks forreceiving the liquid effluent and separating it by sedimentary depositinto a collected solid waste component and an outflowing fluid flowingto an exit conduit from which such collected solid waste has beenseparated; comprising (a) a source of controlled pressure differential(e.g. a suction pump with one or more valves or regulators, or anauxiliary effluent pump) that causes or maintains a pressuredifferential between the surge tank inlet and the sedimentary deposittank outlet for causing liquid to flow from the surge tank through thesedimentary deposit tank to the outlet thereof in response to thepressure differential; (b) a bypass conduit connecting the surge tankinlet to the exit conduit; (c) a pressure balancing valve at the surgetank inlet port that facilitates maintenance of the pressuredifferential; (d) the sedimentary deposit tank comprising a series ofbaffle chambers separated by baffle chamber walls, one or more of saidbaffle chambers containing baffles inclined in one or two dimensions forfacilitating deposit of solid particles, the series of baffle chambersbeing structured and arranged so that the first (inlet) baffle chamberreceives the liquid effluent, and the liquid effluent passes in sequencethrough the baffle chambers and exits the final (outlet) baffle chamberas said outflowing fluid.
 2. Apparatus as defined in claim 1 , whereinthe baffles are planar.
 3. Apparatus as defined in claim 1 , wherein thebaffles are chevron-shaped.
 4. Apparatus as defined in claim 1 , whereinthe baffles are gable-shaped.
 5. Apparatus as defined in claim 1 ,wherein the baffles in the baffle chambers are positioned anddimensioned so as to divide each baffle chamber so that in each bafflechamber, effluent passes over or under the baffles in the chamber insequence from inlet to outlet of the chamber.
 6. Apparatus as defined inclaim 5 , wherein the inclined baffles are formed individually andinclude attached flanges or tabs or equivalent to allow the verticalstacking of two or more baffles within a baffle chamber.
 7. Apparatus asdefined in claim 5 , wherein the inclined baffles are formed as multiplebaffle units comprising two or more baffles stacked vertically and heldin vertical separation by integrally formed separation ribs orequivalent.
 8. Apparatus as defined in claim 5 , wherein each of thebaffle walls separating the chambers is open at the top to a heightsubstantially uniform throughout the sedimentary deposit tank. 9.Apparatus as defined in claim 5 , wherein the series of baffle chamberscomprises at least three baffle chambers, and wherein one or more of thefinal two baffle chambers include modular filtration or adsorptioninserts for filtering fine and floating particles or adsorption ofdissolved particles out of the effluent.
 10. Apparatus as defined inclaim 9 wherein the adsorbent material contained in the modularadsorption insert comprises bentonite clay.
 11. Apparatus as defined inclaim 9 wherein the modular adsorption insert contains a porous membranefilled with finely divided bentonite clay mixed with silica sand. 12.Apparatus as defined in claim 5 , additionally comprising one or morechemical agent inlet ports located in the vicinity of the inlet of thesedimentary deposit tank and a chemical agent delivery device connectedthereto for introducing a suitable selected chemical agent (including aselection of suitable and mutually compatible precipitants, flocculantsand/or chelating agents) at a controlled rate into the sedimentarydeposit tank to facilitate removal of dissolved metallic particles outof the liquid such as by means of precipitation, flocculation orchelation.
 13. Apparatus as defined in claim 12 , wherein the chemicalagent delivery device is a chemical agent delivery pump receivingchemical agent from a stored supply thereof and that delivers inoperation a metered amount of chemical agent into the sedimentarydeposit tank while the sedimentary deposit tank is overfull of effluent.14. Apparatus as defined in claim 13 , additionally comprising a liquidlevel sensor coupled to the sedimentary deposit tank near the topthereof for sensing whether the liquid within the surge tank has droppedbelow the top of the sedimentary deposit tank, and wherein the chemicalagent delivery pump is responsive to the liquid level sensor and ceasesoperation when the liquid within the surge tank has dropped below thetop of the sedimentary deposit tank.
 15. Apparatus as defined in claim 1, wherein the sedimentary deposit tank is a modular unit removablyconnected between the surge tank and the exit conduit.
 16. Apparatus asdefined in claim 15 , additionally comprising an auxiliary filtrationdevice coupled to and downstream of the outlet of the sedimentarydeposit tank for receiving liquid from the sedimentary deposit tank andfiltering from liquid passing therethrough at least some of anyremaining solid particles, and is removable and replaceable as a modularunit independently or together with the sedimentary deposit tank. 17.Apparatus as defined in claim 1 additionally comprising a liquid levelsensing probe coupled to the surge tank for sensing whether the liquidwithin the surge tank has risen to at least one predetermined thresholdlevel, and additionally comprising a signalling device responsive to theliquid level sensor for providing a signal when liquid in the surge tankexceeds such threshold level.
 18. Apparatus as defined in claim 1 ,wherein the source of controlled pressure differential includes a vacuumpump connected to the exit conduit downstream thereof.
 19. Apparatus asdefined in claim 1 , wherein the source of controlled pressuredifferential includes an auxiliary effluent pump connected to the outletport downstream of the sedimentary deposit tank.
 20. Apparatus asdefined in claim 1 , wherein the source of controlled pressuredifferential includes an auxiliary effluent pump connected between thesurge tank and the sedimentary deposit tank.
 21. Apparatus as defined inclaim 1 , wherein the source of controlled pressure differential is asuction pump and wherein the pressure balancing valve is a vacuum breakvalve connected to the bypass conduit in the vicinity of the surge tankinlet port.
 22. Apparatus as defined in claim 21 , wherein the vacuumbreak valve is biased closed and opens to the ambient air in response toa drop in pressure in the adjacent portion of the bypass conduit. 23.Apparatus as defined in claim 1 , additionally comprising at least onesuction apparatus providing a partial vacuum in an effluent sourceconduit upstream of the surge tank, which said effluent conduit passesthe liquid effluent into the surge tank, said suction apparatusconstituting at least a portion of the fluid driving means. 24.Apparatus as defined in claim 17 , wherein the suction apparatus isdental office suction apparatus.
 25. Apparatus as defined in claim 1 ,wherein the bypass conduit has an upper subconduit for passing air and alower subconduit for passing liquid.
 26. Apparatus as defined in claim 1comprising a plurality of sedimentary deposit tanks that become full atstaggered intervals, having means for selectably connecting anddisconnecting each of the sedimentary deposit tanks to the surge tankthereby to selectably route effluent through one or more selectedsedimentary deposit tanks, additionally including a suction attachmentconnected to the inlet port of the surge tank and selectably connectableto the outlet port of any selected one of the sedimentary deposit tanksfor removing excess liquid effluent from such selected sedimentarydeposit tank that has been disconnected from the surge tank. 27.Apparatus as defined in claim 1 , additionally including an air circuitcoupled to the air bypass conduit for drying a full sedimentary deposittank that has been removed from direct connection to the surge tank andreceives no input effluent, wherein such circuit is removably connectedto the inlet and outlet ports of a full sedimentary deposit tank to bedried, and whereby air passing through the bypass conduit is selectablydiverted to flow through the full sedimentary deposit tank to be dried.28. Apparatus as defined in claim 1 , additionally including a mercuryvapour filter coupled into the bypass conduit and removing mercury fromthe air flowing therethrough.
 29. Apparatus as defined in claim 1 ,additionally including flow rate control means (such as a needle valve)connected to the output of the sedimentary deposit tank for controllingthe rate of fluid flow out of the sedimentary deposit tank. 30.Apparatus as defined in claim 1 , additionally including a solids levelsensor coupled to the sedimentary deposit tank for warning that solidswithin the sedimentary deposit tank in the vicinity of the solids levelsensor have reached a threshold level.
 31. Apparatus as defined in claim1 , additionally comprising a bypass conduit connection valve connectedbetween the top of the surge tank and the bypass conduit connected tothe top of the surge tank via an intermediate valve, and an airinjection port for controllably injecting air under pressure into thesurge tank, whereby positive air pressure thus injected may serve atleast in part as the source of the pressure differential.
 32. Apparatusas defined in claim 1 , wherein two or more sedimentary deposit tanksare detachably coupled together in series, the first sedimentary deposittank in the series receiving effluent from the outlet of a surge tank,and passing effluent to the next sedimentary deposit tank, seriatimuntil the effluent reaches the last sedimentary deposit tank in theseries which passes the effluent to the exit conduit.
 33. Apparatus asdefined in claim 1 , wherein two or more sedimentary deposit tanks aredetachably coupled together in parallel, the inlet ports of eachsedimentary deposit tank connected to a common surge tank, receivingeffluent from the surge tank, and the outlet ports of each sedimentarydeposit tank connected to the common exit conduit.
 34. Apparatus asdefined in claim 1 , wherein the outlet port located at the top of thesedimentary deposit tank includes an outlet pipestem and protectivesleeve assembly depending downwardly therefrom where the protectivesleeve assembly extends below the end of the outlet pipestem to preventfloating debris or froth from being drawn into the pipestem and exitingthe sedimentary deposit tank through the outlet port.
 35. Apparatus forseparating metallic particles from liquid effluent flowing from a sourcethereof, including two or more surge tanks coupled in parallel to asource of such effluent, for collecting a quantity of effluentcontaining such metallic particles; and two or more sedimentary deposittanks associated with the surge tanks for receiving the liquid effluentand separating it by sedimentary deposit into a collected solid wastecomponent and an out-flowing fluid flowing to an exit conduit from whichsuch collected solid waste has been separated; comprising (a) a sourceof controlled pressure differential (e.g. an auxiliary effluent pump)creating a pressure differential between the surge tank inlet and thesedimentary deposit tank outlets for causing liquid to flow from thesurge tank through the sedimentary deposit tanks to the outlets thereofin response to the pressure differential; (b) a bypass conduitconnecting the surge tank inlet to the exit conduit; (c) a source ofcontrolled vacuum pressure (e.g. a suction pump with one or more valvesor regulators) between the effluent source and the exit conduit, forcausing liquid to flow from the effluent source into the surge tankunder suction, and air to flow from the effluent source into the exitconduit via the surge tank inlet; (d) a pressure balancing valve at thesurge tank inlet port that facilitates maintenance of the vacuumpressure; (e) each said sedimentary deposit tank comprising a series ofbaffle chambers separated by baffle chamber walls, one or more of saidbaffle chambers containing baffles inclined in one or two dimensions forfacilitating deposit of solid particles, the series of baffle chambersbeing structured and arranged so that the first (inlet) baffle chamberreceives the liquid effluent, and the liquid effluent passes in sequencethrough the baffle chambers and exits the final (outlet) baffle chamberas said outflowing fluid.
 36. Apparatus as defined in claim 35 , whereinthe source of the pressure differential is an auxiliary effluent pumpsituated downstream of the sedimentary deposit tanks, drawing treatedeffluent from the outlet port of each sedimentary deposit tank, anddischarging the effluent into a common effluent drain.
 37. Apparatus asdefined in claim 35 , wherein the source of the pressure differentialacross the sedimentary deposit tanks is two or more auxiliary effluentpumps situated downstream of each said surge tank, between such surgetank and associated sedimentary deposit tanks.